For more than thirty years, vascular diseases have been treated using open surgical procedures. In 1999 alone, 753,000 open-heart procedures, including coronary artery bypass grafting (CABG), valve replacements, and heart transplants, were performed. During a typical CABG procedure, a sternotomy is performed to gain access to the pericardial sac, the patient is put on cardiopulmonary bypass (CPB), and the heart is stopped using a cardioplegia solution.
Generally, previously-known CPB is accomplished by constructing an extracorporeal blood handling system including, inter alia, a venous line, a venous reservoir, a centrifugal or roller pump that perfuses blood through the extracorporeal circuit and the patient, an oxygenator for oxygenating the blood, an arterial line for returning oxygenated blood to the patient, and an arterial filter located in the arterial line.
Many extracorporeal blood handling systems also include a heat exchanger. Heat exchangers are generally used to cool the blood and lower the patient's body temperature during surgery. Reducing body temperature significantly lowers the demand for oxygen by the patient's vital organs. The blood is heated near the end of surgery to raise the body temperature.
Recently, the development of minimally invasive techniques for cardiac bypass grafting, for example, by Heartport, Inc., Redwood City, Calif., and CardioThoracic Systems, Inc., Cupertino, Calif., have placed a premium on reducing the size of equipment employed in the sterile field. Whereas open surgical techniques typically provide a relatively large surgical site that the surgeon views directly, minimally invasive techniques require the placement of endoscopes, video monitors, and various positioning systems for the instruments. These devices crowd the sterile field and can limit the surgeon's ability to maneuver.
At the same time, however, the need to reduce priming volume of the oxygenator and pump, and the desire to reduce blood contact with non-native surfaces has increased interest in locating the oxygenator and pump as near as possible to the patient.
In recognition of the foregoing issues, some previously known extracorporeal blood handling systems have attempted to miniaturize and integrate components including an oxygenator, heat exchanger and pump.
One problem with previously known extracorporeal blood handling systems is the difficulty in designing an extracorporeal blood handling system including an integrated heat exchanger having improved heat transfer efficiency.
Another problem with previously known extracorporeal blood handling systems is that the inclusion of an integrated heat exchanger necessitates additional priming volume.
A further problem with previously known extracorporeal blood handling systems is the difficulty in designing an extracorporeal blood handling system having an integrated heat exchanger that is integrated in such a way as to minimize the overall size of the extracorporeal blood handling system.
In view of the aforementioned limitations, it would be desirable to provide an extracorporeal blood handling system including an integrated heat exchanger having improved heat transfer efficiency.
It also would be desirable to provide an extracorporeal blood handling system including an integrated heat exchanger that does not require additional priming volume.
It would be also be desirable to provide an extracorporeal blood handling system including an integrated heat exchanger that is integrated in such a way as to minimize the overall size of the blood handling system.
It further would be desirable to provide an extracorporeal blood handling systems wherein the integrated heat exchanger provides dual functionality as a blood filter and a heat exchanger.